以下程序段运行后，输出应为？

int a, b;
for (a = 1, b = 1; a <= 100; a++) {
    if (b > 20)
        break;
    if (b % 4 == 1) {
        b = b + 4;
        continue;
    }
    b = b - 5;
}
cout << a;